The invention is based on a position-fixing device as described by the preamble to the main claim.
In fuel injection pumps of the series type, it is necessary to measure the supply onset position, for instance, or a rotary position corresponding to supply onset, of the first cam (that is, the first cam after the drive means) of the camshaft which here serves as the drive shaft, and subsequently to fix the camshaft in position in order to be able to mount the injection pump on the appropriately readied internal combustion engine. In the case of fuel injection pumps of the distributor type, the drive shaft is fixed in the rotary position in which a predetermined recess begins to perform supply, or else it is held blocked in a position which is displaced by a constant amount from this rotary position.
In order to identify this supply onset position which is ascertained on the test bench, it is known to place a second slash mark on the end face of the pump which agrees with a first slash mark on some element which is firmly connected with the drive shaft, or to provide a slash mark on the movable element if the fixed mark is located on the pump housing. This known manner of initial adjustment has the grave disadvantage, among others, that the slash marking either cannot be seen from outside, or is difficult to see, if the pump is mounted with an end flange on the gear boxes of the engine. It this case, it is frequently necessary to search for the supply onset once again after the pump has been mounted on the engine. This can be done by the so-called "overflow method", in which with the pressure valve removed the pump suction chamber is placed under fuel pressure and the pump is slowly pivoted, with the drive shaft coupled to it and fixed in position, until the pump piston closes the intake bore during its upward stroke and the fuel ceases to flow out. In this position, the injection pump is firmly screwed to the engine, which is already set to supply onset. This adjustment is very wasteful of time and can be performed only by experienced technical personnel. However, even when the slash mark is accessible, the accuracy of this adjustment done while the pump is being mounted on the motor depends to a considerable extent on the skill of the mechanic.
Devices of the general type described by the preamble to the main claim are also known (from the German Offenlegungsschrift No. 20 00 997) or corresponding U.S. Pat. No. 3,702,577 in which the holder pin of an apparatus which is positionally fixed relative to the pump housing is pressed, in the manner of an index pin, into a notch on the circumference of an element connected with the camshaft of the injection pump, in order to lock the camshaft in the supply onset position until it is mounted on the engine. This apparatus serves solely as a means of securing the camshaft in the supply onset position while it is moved, and also makes it possible to reproduce this position later; however, this position is associated only with the "static supply onset".
However, since when the engine is running the "dynamic supply onset" differs from the static supply onset ascertained by the overflow method, it is desirable to be able to establish or subsequently test the dynamic supply onset of the injection pump, preferably at a fixed rpm, not only during initial adjustment at the factory but also when the pump is mounted on the engine and when it is later tested in service (in the course of repairs). Here, again, the supply onset position must be mechanically fixed in order to mount the injection pump on the engine. With known testing and position-fixing devices, this can be realized either not at all or only at great expense in terms of time and cost.